The present invention relates to the installation of electrical conductors to junction boxes and, in particular, to a molded bulkhead bushing for protecting and restraining the conductors in a fashion which facilitates the initial mounting of the conductors and accommodates possible future expansion.
As labor costs increase for the installation of new and remodeling of old electrical supply systems, a need exists for improved wiring devices to facilitate installation, yet accommodate expansion, should future needs require the stringing of additional conductors. Depending upon the application and relevant electrical code, various wiring techniques are employed; although with greater frequency, for both commercial and residential installations, nonmetallic conductors are being strung in lieu of rigidwalled, conductor-receiving conduits. This type of installation, in turn, creates the necessity of mounting a bushing of some type at each junction box to protect the wiring as it passes through the box wall. Provisions must also be made to restrain the conductors at or near the bushing to minimize possible flexion and abrasion of the insulative coverings of the conductors and resultant shorting or grounding of the conductors.
Heretofore, a variety of cast aluminum or zinc bushing/box connectors have been used which essentially comprise a tubular member having a threaded, nut-receiving end which secures the bushing to the box and an outer arcuate end which includes a threaded band clamp for compressively clamping the wire to the arcuate collar to restrain same.
One known plastic bushing of which Applicant is aware is shown in U.S. Pat. No. 3,493,205. There an insulative plastic tubular bushing is disclosed which includes a multifingered flexible end which upon inserting the tapered fingers through a provided hole, expand to secure the bushing to the box. The conductors are secured to the bushing via a serrated wedging member which mounts in a slotted channel formed in the bushing sidewalls at a transverse angle to the conductors. Once mounted, however, the wedging member is removable only with great difficulty. Yet another bushing is disclosed in U.S. Pat. No. 3,788,582 which provides for a rotatable cam member to secure the conductors to the bushing. The manner of securing the conductors to the bushing of each of the foregoing devices is, however, believed distinguishable from the present invention.